#include<iostream>
#include<vector>
#include<unordered_set>
using namespace std;

class Solution {
public:
	bool containsDuplicate(vector<int>& nums) {
		unordered_set<int> s;
		for (int x : nums) {
			if (s.find(x) != s.end()) {
				return true;
			}
			s.insert(x);
		}
		return false;
	}
};


void main() {

}